Methodology

In order to celebrate the tools we use every day, Forbes.com has counted down the 20 most important tools of all time. It's a look at the devices that have most impacted human civilization and helped shape the course of history.

In order to tackle such a huge subject, we first had to limit the scope of our investigation. In consultation with a panel of experts, we came up with the following:

For our purposes, we decided to define a tool as a material device that provides an advantage in accomplishing a task. That eliminated things like language and software.

We decided to exclude the traditional list of "simple machines," which includes the lever, pulley, wheel and wedge, since most other tools employ some form of simple machine--a hammer is basically a lever, and an axe is essentially a wedge.

We tried where possible to limit the list to handheld or easily portable objects, eliminating most heavy machine tools, like hydraulic jacks.

We also decided to eliminate complex machines capable of essentially running themselves. That means things like cars, windmills and computer networks don't qualify.

Using those guidelines, we eventually came up with a list of more than 100 candidate tools. There was a great deal of overlap, so we collapsed similar items into a single category, and chose one tool to represent them. That left us with a final list of 33 items, each one a part of a particular class or style of tool; for instance, the spoon is representative of all eating utensils.

In July, we polled Forbes.com readers for their choice of the top tools. More than 3,000 readers responded. We then surveyed ten senior editors at Forbes.com asking them to rank their top 20. Two of our experts cast votes as well. The final rankings are a weighted-average of experts', editors' and readers' picks.

Our Expert Panel Included:

Don Norman is co-founder of the Nielsen Norman Group, a professor at Northwestern University and former vice president at Apple Computer. He serves on many advisory boards, including Chicago’s Institute of Design and Encyclopedia Britannica. His books include The Design of Everyday Things and Emotional Design.

Henry Petroski is Aleksandar S. Vesic professor of civil engineering and professor of history at Duke University. He is author of the books The Pencil: A History of Design and Circumstance and The Evolution of Useful Things. He also was writer and presenter of the 1987 BBC-television documentary, To Engineer Is Human, which has been broadcast on PBS, and writes the engineering column for American Scientist.

Edward Tenner is a senior research associate of the Jerome and Dorothy Lemelson Center for the Study of Invention and Innovation at the National Museum of American History, and a researcher at Princeton University. His books include Why Things Bite Back: Technology and the Revenge of Unintended Consequences and Our Own Devices: The Past and Future of Body Technology.